Typically, in a wind turbine generator, wind speed and wind direction are measured using an anemometer and an anemoscope provided on a nacelle and are used as control parameters in operation control. However, since such wind speed and wind direction are measured at the downstream side of a rotor, the wind speed of the incoming wind is reduced and the wind direction drifts, thus causing a problem in the measurement accuracy.
Accordingly, for example, in a “wind turbine generator system” disclosed in Japanese Unexamined Patent Application, Publication No. HEI-11-159436, a Doppler radar employing radio waves is used to measure a wind vector from in front of the rotor of a wind turbine generator, the output value from the wind turbine generator is predicted from the wind vector, and output power control of a power generator at an electric-power system is carried out on the basis of the predicted output value.
[Patent Document 1]    Japanese Unexamined Patent Application, Publication No. HEI-11-159436